Pneumatic tire including inner liner

ABSTRACT

A pneumatic tire including an inner liner made of a polymer sheet is provided, and the polymer sheet is made of a polymer composition. The polymer composition includes a polymer component of a styrene-isobutylene-styrene triblock copolymer by greater than or equal to 5 mass % and less than or equal to 80 mass %, and a rubber component of at least one kind selected from the group consisting of natural rubber, isoprene rubber, and isobutylene-isoprene rubber by greater than or equal to 20 mass % and less than or equal to 95 mass %. The polymer composition includes sulfur by greater than or equal to 0.1 mass parts and less than or equal to 5 mass parts with respect to the polymer component by 100 mass parts. The polymer sheet has a thickness T1 of 0.6 mm&lt;T1≤4.0 mm.

TECHNICAL FIELD

The present invention relates to a pneumatic tire including an innerliner.

BACKGROUND ART

In recent years, a weight reduction of a tire has been attempted inaccordance with strong social requests with respect to a reduction offuel consumption for a vehicle. Among tire members, a weight reductionhas been attempted also for an inner liner which is arranged on an innerside of a tire in a radial direction and serves to improve an airpermeation resistance by reducing an amount of leakage of air frominside to outside of a pneumatic tire (air permeation amount).

Currently, as a rubber composition for an inner liner, butyl-basedrubber containing isobutylene-isoprene rubber by 70 to 100 mass % andnatural rubber by 30 to 0 mass % is used to improve the air permeationresistance of a tire. Moreover, butyl-based rubber contains isoprene byabout 1 mass % in addition to butylene, and it enables crosslinking withadjacent rubber cojointly with sulfur, vulcanization accelerator, andzinc white. The butyl-based rubber described above requires in a normalblending a thickness of about 0.6 to 1.0 mm for a tire of a passengercar, and a thickness of about 1.0 to 2.0 mm for a tire of a bus and atruck.

Therefore, it has been proposed to use thermoplastic elastomer, which issuperior in an air permeation resistance than butyl-based rubber and iscapable of reducing a thickness of an inner liner layer, for an innerliner to reduce a weight of a tire. However, the thermoplasticelastomer, which has a smaller thickness than butyl-based rubber andexhibits a high air permeation resistance, has less vulcanizationadherence with insulation rubber or carcass rubber adjacent to the innerliner as compared to butyl-based rubber. When an inner liner has a lowvulcanization adherence, an air-in phenomenon occurs in which air isadded between an inner liner and an insulation or a carcass to cause alarge numbers of small bubbles to appear. Since this phenomenon involvessmall dot patterns inside of a tire, it disadvantageously gives animpression to a user that an appearance is not good. Further, since aninsulation or a carcass is peeled from an inner liner due to air as astarting point during traveling, a crack may occur in the inner liner tolower an internal pressure of the tire. Then, the tire may burst in theworst case.

In PTD 1 (Japanese Patent Laying-Open No. 9-165469), a pneumatic tire isproposed which can improve an adhesiveness between an inner liner and arubber composition forming an inner portion of a tire or a carcass layerby forming the inner liner layer with use of nylon having a low airpermeability. However, in this technique, it would be necessary to applyan RFL treatment to a nylon film and thereafter attach a rubber cementcomposed of a rubber composition to form a nylon film layer. Thus, stepsare complicated disadvantageously.

Moreover, an inner liner portion of a pneumatic tire is likely togenerate heat during traveling of a vehicle. Under a high-temperaturecondition, a stiffness is likely to be lowered, and an operationstability may be deteriorated. Thus, in view of the safety, an innerliner capable of improving the operation stability is also requested.

In PTD 2 (Japanese Patent Laying-Open No. 2011-057940), a tire forcompetition is proposed which can improve an operation stability byusing a rubber composition including carbon black by 30 to 110 massparts with respect to a rubber component by 100 mass parts. However, inthis technique, there is a tendency that heat generation duringtraveling is increased due to an increase in a filler, therebyincreasing a rolling resistance.

CITATION LIST Patent Document

-   PTD 1: Japanese Patent Laying-Open No. 9-165469-   PTD 1: Japanese Patent Laying-Open No. 2011-057940

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a pneumatic tireincluding an inner linear having sufficient non-vulcanization stickinessand vulcanization adhesiveness with an adjacent member and exhibiting asuperior air isolation performance, and reducing a rolling resistanceand having a superior operation stability.

Solution to Problem

The present invention is a pneumatic tire including an inner liner madeof a polymer sheet, and the polymer sheet is made of a polymercomposition. The polymer composition includes a polymer component ofstyrene-isobutylene-styrene triblock copolymer by greater than or equalto 5 mass % and less than or equal to 80 mass %, and a rubber componentof at least one kind selected from the group consisting of naturalrubber, isoprene rubber, and isobutylene-isoprene rubber by greater thanor equal to 20 mass % and less than or equal to 95 mass %. The polymercomposition includes sulfur by greater than or equal to 0.1 mass partsand less than or equal to 5 mass parts with respect to the polymercomponent by 100 mass parts. The polymer sheet has a thickness T1 of 0.6mm<T1≤4.0 mm.

The present invention is a pneumatic tire including an inner liner madeof a polymer laminate, and the polymer laminate includes a first layerand a second layer. The first layer is made of a polymer composition,and the polymer composition includes a polymer component of astyrene-isobutylene-styrene triblock copolymer by greater than or equalto 5 mass % and less than or equal to 80 mass %, and a rubber componentof at least one kind selected from the group consisting of naturalrubber, isoprene rubber, and isobutylene-isoprene rubber by greater thanor equal to 20 mass % and less than or equal to 95 mass %. The polymercomposition includes sulfur by greater than or equal to 0.1 mass partsand less than or equal to 5 mass parts with respect to the polymercomponent by 100 mass parts. The second layer includes a thermoplasticresin composition, and the thermoplastic resin composition includessulfur by greater than or equal to 0.1 mass parts and less than or equalto 5 mass parts with respect to thermoplastic elastomer by 100 massparts. The polymer laminate has a thickness T2 of 0.6 mm<T2≤4.0 mm.

Preferably, in the pneumatic tire of the present invention, thethermoplastic elastomer is at least one kind selected from the groupconsisting of a styrene-isoprene-styrene triblock copolymer, astyrene-isobutylene diblock copolymer, a styrene-butadiene-styrenetriblock copolymer, a styrene-isoprene/butadiene-styrene triblockcopolymer, a styrene-ethylene/butene-styrene triblock copolymer, astyrene-ethylene/propylene-styrene triblock copolymer, astyrene-ethylene/ethylene/propylene-styrene triblock copolymer, astyrene-butadiene/butylene-styrene triblock copolymer, and epoxymodified thermoplastic elastomers thereof.

Preferably, in the pneumatic tire of the present invention, thestyrene-isobutylene-styrene triblock copolymer has a weight-averagemolecular weight of greater than or equal to 50,000 and less than orequal to 400,000 and a styrene unit content of greater than or equal to10 mass % and less than or equal to 30 mass %.

Preferably, in the pneumatic tire of the present invention, thestyrene-isoprene-styrene triblock copolymer has a weight-averagemolecular weight of greater than or equal to 100,000 and less than orequal to 290,000 and a styrene unit content of greater than or equal to10 mass % and less than or equal to 30 mass %.

Preferably, in the pneumatic tire of the present invention, thestyrene-isobutylene diblock copolymer has a straight-chain shape, andhas a weight-average molecular weight of greater than or equal to 40,000and less than or equal to 120,000, and a styrene unit content of greaterthan or equal to 10 mass % and less than or equal to 35 mass %.

Preferably, in the pneumatic tire of the present invention, the epoxymodified styrene-butadiene-styrene triblock copolymer has aweight-average molecular weight of greater than or equal to 10,000 andless than or equal to 400,000 and a styrene unit content of greater thanor equal to 10 mass % and less than or equal to 30 mass %.

Preferably, in the pneumatic tire of the present invention, the polymercomposition further includes stearic acid by greater than or equal to 1mass parts and less than or equal to 5 mass parts, zinc oxide by greaterthan or equal to 0.1 mass parts and less than or equal to 8 mass parts,an anti-aging agent by greater than or equal to 0.1 mass parts and lessthan or equal to 5 mass parts, and a vulcanization accelerator bygreater than or equal to 0.1 mass parts and less than or equal to 5 massparts with respect to the polymer component by 100 mass parts.

Preferably, in the pneumatic tire of the present invention, thethermoplastic resin composition further includes stearic acid by greaterthan or equal to 1 mass parts and less than or equal to 5 mass parts,zinc oxide by greater than or equal to 0.1 mass parts and less than orequal to 8 mass parts, an anti-aging agent by greater than or equal to0.1 mass parts and less than or equal to 5 mass parts, and avulcanization accelerator by greater than or equal to 0.1 mass parts andless than or equal to 5 mass parts with respect to the thermoplasticelastomer by 100 mass parts.

Preferably, in the pneumatic tire of the present invention, the secondlayer further includes, in addition to the thermoplastic resincomposition, a rubber component of at least one kind selected from thegroup consisting of natural rubber, isoprene rubber, andisobutylene-isoprene rubber, and includes the rubber content by greaterthan or equal to 20 mass % and less than or equal to 90 mass % withrespect to a sum total of the thermoplastic resin composition and therubber component.

Preferably, in the pneumatic tire of the present invention, a tread ofthe pneumatic tire is made of a rubber composition includingstyrene-butadiene rubber by greater than or equal to 50 mass % in therubber component.

Preferably, in the pneumatic tire of the present invention, the rubbercomposition further includes silica by greater than or equal to 15 massparts and less than or equal to 150 mass parts with respect to therubber component by 100 mass parts, and a silane coupling agent. Thesilane coupling agent is a block copolymer or a random copolymerprepared by copolymerizing a bonding unit A expressed by the followinggeneral formula (1) and a bonding unit B expressed by the followinggeneral formula (2) with respect to a total amount of the bonding unit Aand the bonding unit B with the bonding unit B in a ratio of 1 molar %to 70 molar %, and is included by greater than or equal to 2 mass partsand less than or equal to 20 mass parts with respect to silica of 100mass parts:

(In the formulas, x and y are integers greater than or equal to 1. R₁may be hydrogen, a halogen atom, an alkyl group of branched ornon-branched carbon 1 to 30, an alkenyl group of branched ornon-branched carbon 2 to 30, or an element having an end of the alkylgroup or the alkenyl group substituted by a hydroxyl group or a carboxylgroup. R₂ represents hydrogen, an alkyl group of branched ornon-branched carbon 1 to 30, or an alkenyl group of branched ornon-branched carbon 2 to 30. R₁ and R₂ may form a ring structure.).

Advantageous Effects of Invention

According to the present invention, a pneumatic tire can be providedwhich includes an inner liner having sufficient non-vulcanizationstickiness and vulcanization adhesiveness with an adjacent member andbeing superior in an air isolation performance, and reducing a rollingresistance and having a superior operation stability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view representing a right half ofa pneumatic tire in one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view representing an example of anarrangement of an inner liner in the pneumatic tire.

FIG. 3 is a schematic cross-sectional view representing one example ofan arrangement of an inner liner in the pneumatic tire.

DESCRIPTION OF EMBODIMENTS

<Pneumatic Tire>

A structure of a pneumatic tire in one embodiment of the presentinvention will be described with reference to FIG. 1.

A pneumatic tire 1 may be used for a passenger car, a truck/bus, and aheavy machinery. Pneumatic tire 1 has a tread portion 2, a side wallportion 3, and a bead portion 4. Further, a bead core 5 is embedded inbead portion 4. Moreover, a carcass 6 provided across one bead portion 4to the other bead portion and having both ends folded to engage withbead core 5, and a belt layer 7 constituted of two plies on an outerside of a crown portion of carcass 6 are arranged. On an inner side ofcarcass 6 in a radial direction of the tire, an inner liner 9 extendingfrom one bead portion 4 to the other bead portion 4 is arranged. Beltlayer 7 is arranged so that two plies constituted of steel cords oraramid fibers intersect each other between the plies to have the cordstypically oriented at the angle of 5 to 30 degrees with respect to thecircumferential direction of the tire. Moreover, the carcass haveorganic fiber cords of polyester, nylon, aramid, or the like disposed atapproximately 90° in the circumferential direction, and a bead apex 8extending from an upper end of bead core 5 in the side wall direction isarranged in the region surrounded by the carcass and folded portions ofthe carcass. An insulation may be arranged between inner liner 9 andcarcass 6.

First Embodiment

In one embodiment of the present invention, an inner liner is made of apolymer sheet.

<Polymer Sheet>

The polymer sheet is made of a polymer composition. In the polymercomposition, a polymer component includes a styrene-isobutylene-styrenetriblock copolymer (in the following, also referred to as “SIBS”) bygreater than or equal to 5 mass % and less than or equal to 80 mass %,and a rubber component of at least one kind selected from the groupconsisting of natural rubber, isoprene rubber, and isobutylene-isoprenerubber by greater than or equal to 20 mass % and less than or equal to95%. Further, the polymer composition includes sulfur by greater than orequal to 0.1 mass parts and less than or equal to 5 mass parts withrespect to the polymer component by 100 mass parts.

(Polymer Composition)

The polymer composition includes SIBS, a rubber component, and sulfur.When the rubber component and sulfur are added to the SIBS and thenheated and mixed, a vulcanization reaction occurs between the rubbercomponent and sulfur during heating and mixing, so that a sea-islandstructure is formed which has SIBS as a matrix (sea) and the rubbercomponent as an island.

The polymer composition having the sea-island structure has an airisolation performance derived from a matrix phase of SIBS. The rubbercomponent forming an island phase has a non-vulcanization stickinesswith an adjacent member including a rubber component. Moreover, since avulcanization reaction with the rubber component of an adjacent memberoccurs during heating and mixing, it also has a vulcanizationadhesiveness with an adjacent member. Thus, the polymer sheet made ofthe polymer composition is superior in an air isolation performance aswell as a non-vulcanization stickiness and a vulcanization adhesivenesswith an adjacent member.

(Styrene-Isobutylene Triblock Copolymer)

The isobutylene block of SIBS provides a superior air permeationresistance to a polymer sheet including the SIBS. Thus, when a polymersheet including SIBS is used for an inner liner, a pneumatic tire havinga superior air permeation resistance can be obtained.

Further, since a molecular structure of SIBS other than aromatic seriesis completely saturated, deterioration hardening is suppressed, and asuperior durability is provided. Thus, when a polymer sheet includingSIBS is used for an inner liner, a pneumatic tire having a superiordurability can be obtained.

When a pneumatic tire is manufactured by applying a polymer sheetincluding SIBS to an inner liner, the inclusion of SIBS assures an airpermeation resistance. Therefore, high-density halogenated rubber suchas halogenated isobutylene-isoprene rubber having been conventionallyused for providing an air permeation resistance is not used. Even whenthe high-density halogenated rubber is used, the amount of use can bereduced. Accordingly, a tire can be light-weighted, and an effect ofimproving fuel consumption can be obtained.

A molecular weight of the SIBS is not particularly limited. However, inview of a fluidity, a molding step, and a rubber elasticity, it ispreferable that a weight-average molecular weight according to the GPCmethod is greater than or equal to 50,000 and less than or equal to400,000. When the weight-average molecular weight is less than 50,000, atensile strength and a tensile elongation are likely to be lowered. Whenthe weight-average molecular weight exceeds 400,000, an extrusionperformance may be deteriorated. Thus, it is not preferable.

SIGBS generally includes a styrene unit of greater than or equal to 10mass % and less than or equal to 40 mass %. On the point that an airpermeation resistance and a durability become more favorable, it ispreferable that the content of the styrene unit in SIBS is greater thanor equal to 10 mass % and less than or equal to 30 mass %.

It is preferable that SIBS has a molar ratio of an isobutylene unit anda styrene unit (isobutylene unit/styrene unit) of 40/60 to 95/5 in viewof the rubber elasticity of the copolymer. In SIBS, it is preferablethat a degree of polymerization of each block is approximately 10,000 to150,000 in an isobutylene block (it is liquefied when the degree ofpolymerization is less than 10,000) and 5,000 to 30,000 in a styreneblock in view of the rubber elasticity and handling.

SIBS can be obtained by a general method for polymerizing a vinyl-basedcompound. For example, it can be obtained by a living cationicpolymerization method.

Japanese Patent Laying-Open No. 62-48704 and Japanese Patent Laying-OpenNo. 64-62308 disclose that the living cationic polymerization ofisobutylene and other vinyl compound can be conducted, and that apolyisobutylene-based block copolymer can be manufactured by usingisobutylene and other compound for a vinyl compound. Other than thosedescribed above, methods for manufacturing a vinyl compound with use ofthe living cationic polymerization method are disclosed in, for example,U.S. Pat. No. 4,946,899, U.S. Pat. No. 5,219,948, and Japanese PatentLaying-Open No. 3-174403.

Since SIBS does not have a double bond other than the aromatic series ina molecule, a stability with respect to an ultraviolet radiation ishigher and a weather resistance is better than a polymer such aspolybutadiene having a double bond in a molecule.

The content of SIBS is greater than or equal to 5 mass % and less thanor equal to 80 mass % in the polymer component of the polymercomposition. When the content of SIBS is less than 5 mass %, an airisolation performance of the polymer sheet may be lowered. On the otherhand, when the content of SIBS exceeds 80 mass %, a vulcanizationadhesiveness with an adjacent member may be insufficient. In view ofassuring the air isolation performance, the content of SIBS in thepolymer component is preferably greater than or equal to 10 mass %, morepreferably less than or equal to 40 mass %, and yet more preferably lessthan or equal to 30 mass %.

(Rubber Component)

In First Embodiment, the polymer composition constituting the polymersheet includes a rubber component. The rubber component can provide thepolymer composition with a non-vulcanization stickiness with an adjacentmember including a rubber component. Further, a vulcanization reactionwith sulfur can provide the polymer composition with a vulcanizationadhesiveness with an adjacent member such as a carcass or an insulation.

The rubber component includes at least one kind selected from the groupconsisting of natural rubber, isoprene rubber, and isobutylene-isoprenerubber. Among those, it is preferable to include natural rubber in viewof a fracture strength and an adhesiveness.

The content of the rubber component is greater than or equal to 20 mass% and less than or equal to 95 mass % in the polymer component of thepolymer composition. When the content of the rubber component is lessthan 20 mass %, a viscosity of the polymer composition is raised, and anextrusion performance is deteriorated. Therefore, a polymer sheet is notto be thinned at the time of manufacturing the polymer sheet. On theother hand, when the content of the rubber component exceeds 95 mass %,the air isolation performance of the polymer sheet may be lowered. Inview of the non-vulcanization stickiness and the vulcanizationadhesiveness, the content of the rubber component in the polymercomponent is preferably greater than or equal to 60 mass %, morepreferably greater than or equal to 70%, and preferably less than orequal to 90 mass %.

(Sulfur)

In First Embodiment, the polymer composition constituting the polymersheet includes sulfur.

As sulfur, sulfur generally used in a rubber industry at the time ofvulcanization may be used. Particularly, it is preferable to useinsoluble sulfur. The insoluble sulfur is sulfur having a high molecularweight of Sx (x=100,000 to 300,000) by heating and quenching naturalsulfur S8. Using the insoluble sulfur can prevent blooming whichgenerally occurs when sulfur is used as a rubber vulcanizing agent.

The content of sulfur is greater than or equal to 0.1 mass parts andless than or equal to 5 mass parts with respect to the polymer componentby 100 mass parts. When the content of sulfur is less than 0.1 massparts, a vulcanizing effect of the rubber component cannot be obtained.On the other hand, when the content of sulfur exceeds 5 mass parts, ahardness of the polymer composition increases. Therefore, when thepolymer sheet is used for the inner liner, a durability of the pneumatictire is likely to be lowered. More preferably, the content of sulfur isgreater than or equal to 0.3 mass parts and less than or equal to 3.0mass parts.

(Additive of Polymer Composition)

In First Embodiment, the polymer composition constituting the polymersheet can include an additive such as stearic acid, zinc oxide, ananti-aging agent, a vulcanization accelerator, or the like.

The stearic acid serves as a vulcanization assistant for the rubbercomponent. The content of the stearic acid is preferably greater than orequal to 1 mass parts and less than or equal to 5 mass parts withrespect to the polymer component by 100 mass parts. When the content ofthe stearic acid is less than 1 mass parts, an effect as a vulcanizationassistant cannot be obtained. On the other hand, when the content of thestearic acid exceeds 5 mass parts, a viscosity of the polymercomposition is lowered, and a fracture strength is lowered, thus it isnot preferable. More preferably, the content of the stearic acid isgreater than or equal to 1 mass parts and less than or equal to 4 massparts.

Zinc oxide serves as a vulcanization assistant of the rubber component.The content of zinc oxide is preferably greater than or equal to 0.1mass parts and less than or equal to 8 mass parts with respect to thepolymer component by 100 mass parts. When the content of zinc oxide isless than 0.1 mass parts, an effect as a vulcanization assistant cannotbe obtained. On the other hand, when the content of zinc oxide exceeds 8mass parts, a hardness of the polymer composition is raised. Therefore,when the polymer sheet is used for the inner liner, a durability of thepneumatic tire may be lowered. More preferably, the content of zincoxide is greater than or equal to 0.5 mass parts and less than or equalto 6 mass parts.

The anti-aging agent has a function of preventing a series ofdeterioration such as oxidation deterioration, heat deterioration, ozonedeterioration, and fatigue deterioration, which are called aging. Theanti-aging agent is grouped into a primary anti-aging agent includingamines and phenols, and a secondary anti-aging agent including a sulfurcompound and phosphites. The primary anti-aging agent has a function ofproviding hydrogen to various polymer radicals and stopping a chainreaction of autoxidation, and the secondary anti-aging agent exhibits astabilizing action of changing hydroxy peroxide into stable alcohol.

The anti-aging agent includes amines, phenols, imidazoles, phosphoros,and thio urea.

The amines include phenyl-α-naphthylamine, a2,2,4-trimethyl-1,2-dihydroquinoline polymer,6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, p,p′-dioctyldiphenylamine, p,p′-dicumyl diphenylamine,N,N′-di-2-naphthyl-p-phenylenediamine, N,N′-diphenyl-p-phenylenediamine,N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and the like.

Phenols include 2,6-di-tert-butyl-4-methyl phenol,2,6-di-tert-butyl-4-methyl phenol, stirenated methyl phenol,2,2′-methylene bis(4-ethyl-6-tert-butyl phenol), 2,2′-methylenebis(4-methyl-6-tert-butyl phenol), 4,4′-butylidenebis(3-methyl-6-tert-butyl phenol), 4,4-thio bis(3-methyl-6-tert-butylphenol), 2,5-di-tert-butyl hydroquinone, 2,5-di-tert-amyl hydroquinone,and the like.

Imidazoles include 2-mercaptobenzimidazole, zinc salt of2-mercaptobenzimidazole, dibutyl dithiocarbamate nickel, and the like.

Other than those described above, phosphorous such as tris(nonylatedphenyl)phosphite, thio urea such as 1,3-bis(dimethylaminopropyl)-2-thiourea, and tributyl thio urea, ozone deterioration prevention wax, andthe like may be used.

The anti-aging agents described above may be used individually with onekind or in combination of two or more kinds. Among those, it ispreferable to use N-(1,3-dimethyl butyl)-N′-phenyl-p-phenylenediamine.

Preferably, it is preferable that the content of the anti-aging agent isgreater than or equal to 0.1 mass parts and less than or equal to 5 massparts with respect to the polymer component by 100 mass parts. When thecontent of the anti-aging agent is less than 0.1 mass parts, theanti-aging effect cannot be obtained. On the other hand, when thecontent of the anti-aging agent exceeds 5 mass parts, a bloomingphenomenon occurs in the polymer composition. It is more preferable thatthe content of the anti-aging agent is greater than or equal to 0.3 massparts and less than or equal to 4 mass parts.

As the vulcanization accelerator, thiurams, thiazoles, thio urea,dithiocarbamates, guanidines, sulfenamides, and the like can be used.

The thiurams include tetramethyl thiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutyl thiuramdisulfide, dipentamethylene thiuram tetrasulfide, and the like.

The thiazoles include 2-mercaptobenzothiazole, dibenzothiadyl disulfide,N-cyclohexyl benzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide,N-oxydiethylene-2-benzothiazole sulfenamide,N-tert-butyl-2-benzothiazole sulfenamide,N,N-dicyclohexyl-2-benzothiazole sulfenamide,N-tert-butyl-2-benzothiazolyl sulfenamide, and the like.

The thio urea includes N,N′-diethyl thiourea, ethylene thio urea,trimethyl thio urea, and the like.

The dithiocarbamates include dimethyl dithiocarbamate zinc, diethyldithiocarbamate zinc, dibutyl dithiocarbamate zinc, dimethyldithiocarbamate sodium, diethyl dithiocarbamate sodium, dimethyldithiocarbamate copper, dimethyl dithiocarbamate iron III), diethyldithiocarbamate selenium, diethyl dithiocarbamate tellurium, and thelike.

The guanidines include di-o-tolylguanidine, 1,3-diphenylguanidine,1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, andthe like.

The sulfenamides include N-cyclohexyl-2-benzothiazilsulfenamide, and thelike.

The vulcanization accelerator described above may be used individuallywith one kind or in combination of two or more kinds. Among those, it ispreferable to use dibenzothiazyl disulfide.

Preferably, the content of the vulcanization accelerator is greater thanor equal to 0.1 mass parts and less than or equal to 5 mass parts withrespect to the polymer component by 100 mass parts. When the content ofthe vulcanization accelerator is less than 0.1 mass parts, thevulcanization accelerating effect cannot be obtained. On the other hand,when the content of the vulcanization accelerator exceeds 5 mass parts,a hardness of the polymer composition is raised. Therefore, when thepolymer sheet is used for the inner liner, a durability of the pneumatictire may be lowered. Further, the raw material cost of the polymercomposition is raised. More preferably, the content of the vulcanizationaccelerator is greater than or equal to 0.3 mass parts and less than orequal to 4 mass parts.

(Thickness of Polymer Sheet)

In First Embodiment, the polymer sheet has a thickness T1 of 0.6mm<T1≤4.0 mm. When the thickness of the polymer sheet is less than orequal to 0.6 mm, a favorable operation stability cannot be obtained inthe pneumatic tire having the polymer sheet applied to the inner liner.

On the other hand, when the thickness of the polymer sheet exceeds 4.0mm, a tire weight and a rolling resistance are increased, so that lowfuel consumption performance is lowered. It is preferable that thethickness of the polymer sheet is greater than or equal to 0.8 mm andless than or equal to 3.8 mm.

(Method for Manufacturing Polymer Sheet)

In First Embodiment, the polymer sheet can be manufactured, for example,by the following method. Each compounding agent is placed into atwo-axis extruder and kneaded under the condition of about 150 to 280°C. and 50 to 300 rpm to obtain a pellet of a polymer composition havingdynamically crosslinked SIBS, rubber component, sulfur, and variousadditives as needed. The obtained pellet is placed into a T-die extruderto obtain a polymer sheet having a desired thickness.

In the two-axis extruder, SIBS as a thermoplastic resin compositionattains a matrix phase, and the rubber component attains an islandphase. Then, they are dispersed. Further, in the two-axis extruder, therubber component and the additive component react with each other, sothat a crosslinking reaction occurs in the rubber component in an islandphase. Since the rubber component is dynamically crosslinked in thetwo-axis extruder, it is called dynamic crosslinking. Even when therubber component crosslinks in the two-axis extruder, since the matrixphase of the system is composed of the thermoplastic resin component, ashear viscosity is low in the whole system, and extrusion can beconducted.

The pellet of the dynamically crosslinked polymer composition obtainedby the two-axis extruder includes the crosslinked rubber component.However, the thermoplastic resin component in the matrix phase maintainsits plasticity and serves to provide a plasticity for the whole system.Therefore, since the plasticity is exhibited in the T-die extrusion, itcan be formed into a sheet-like shape.

Further, since the pallet of the dynamically crosslinked polymercomposition has the crosslinked rubber component, intrusion of thepolymer composition of the inner liner to the carcass layer can beprevented even when the polymer sheet manufactured with use of thepellet is applied to the inner layer and the pneumatic tire is heated atthe time of manufacturing the pneumatic tire.

<Tread>

In one embodiment of the present invention, it is preferable that thetread of the pneumatic tire is made of the rubber composition includingstyrene-butadiene rubber (in the following, also referred to as “SBR”)by greater than or equal to 50 mass % in the rubber component.

The SBR is not particularly limited, and SBR generally used in a tireindustry such as emulsion-polymerized styrene-butadiene rubber (E-SBR),solution-polymerized styrene-butadiene rubber (S-SBR), and the like canbe used. Among those, S—SBR is preferable.

The styrene unit content of the SBR is preferably greater than or equalto 25 mass %, and more preferably greater than or equal to 35 mass %.When the content is less than 25 mass %, there is a tendency that asufficient wet-grip performance cannot be obtained. Moreover, thestyrene component content is preferably less than or equal to 60 mass %,and more preferably less than or equal to 50 mass %. There is a tendencythat a wear resistance is lowered when the content exceeds 60 mass %.The styrene component content of the SBR is calculated by the 1H-NMRmeasurement.

The content of the SBR in the rubber component by 100 mass % ispreferably greater than or equal to 50 mass %, more preferably greaterthan or equal to 70 mass %, and yet more preferably greater than orequal to 80 mass %. There is a tendency that a sufficient wet-gripperformance cannot be obtained when the content is less than 50 mass %.Moreover, an upper limit of the content of SBR is not particularlylimited, and it may be 100 mass %.

As the rubber component other than SBR, there may be used, for example,natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR),styrene isoprene butadiene rubber (SIBR), ethylene propylene dienerubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber(NBR), isobutylene-isoprene rubber (IIR), and the like. These rubbercomponents may be used individually or in combination of two or morekinds.

The tread rubber composition preferably includes silica. Accordingly,the wet-grip performance can be improved, and the effect of improvingthe wear resistance and operation stability can be obtained, so that theeffect of the present invention can be obtained more favorably. Silicaincludes, for example, dry silica (anhydrous silica), wet silica(hydrous silica), and the like. Among those, the wet silica ispreferable on the reason that there are many silanol groups.

A nitrogen absorption specific surface area (N₂SA) of silica ispreferably greater than or equal to 40 m²/g, more preferably greaterthan or equal to 70 m²/g, yet more preferably greater than or equal to110 m²/g. There is a tendency that the wear resistance is lowered whenthe area is less than 40 m²/g. Moreover, the N₂SA of silica ispreferably less than or equal to 220 m²/g, and more preferably 200 m²/g.When the area exceeds 220 m²/g, silica becomes less likely to disperse,and the wear resistance may to be deteriorated. The N₂SA of silica is avalue measured by the BET method in accordance with ASTM D3037-93.

The content of silica is preferably greater than or equal to 15 massparts, more preferably greater than or equal to 20 mass parts by therubber component by 100 mass parts. When the content is less than 15mass parts, sufficient wet-grip performance and wear resistance may notbe obtained. The content of the silica is preferably less than or equalto 150 mass parts, more preferably less than or equal to 140 mass parts,yet more preferably less than or equal to 130 mass parts. When thecontent exceeds 150 mass parts, silica becomes less likely to disperse,and the wear resistance may be deteriorated.

When silica is blended to the tread rubber composition, it is preferableto blend a silane coupling agent with silica. The silane coupling agentis not particularly limited, and it may be the silane coupling agentconventionally used with silica in the tire industry.

Particularly, it is preferable to use a silane coupling agent which is ablock copolymer or a random copolymer prepared by copolymerizing abonding unit A expressed by the following general formula (1) and abonding unit B expressed by the following general formula (2) with thebonding unit B in a ratio of 1 molar % to 70 molar % with respect to atotal amount of the bonding unit A and the bonding unit B, and isincluded by greater than or equal to 2 mass parts and less than or equalto 20 mass parts with respect to silica of 100 mass parts:

(In the formula, x and y are integers greater than or equal to 1. R₁ maybe hydrogen, a halogen atom, an alkyl group of branched or non-branchedcarbon 1 to 30, an alkenyl group of branched or non-branched carbon 2 to30, or an element having an end of the alkyl group or the alkenyl groupsubstituted by a hydroxyl group or a carboxyl group. R₂ representshydrogen, an alkyl group of branched or non-branched carbon 1 to 30, oran alkenyl group of branched or non-branched carbon 2 to 30. R₁ and R₂may form a ring structure.)

The silane coupling agent includes, for example, bis(3-triethoxysilylpropyl)polysulfide, bis(2-triethoxysilyl ethyl)polysulfide,bis(3-trimethoxysilyl propyl)polysulfide, bis(2-trimethoxysilylethyl)polysulfide, bis(4-triethoxysilyl butyl)polysulfide,bis(4-trimethoxysilyl butyl)polysulfide, and the like. These silanecoupling agents may be used individually or in combination of two ormore kinds.

The content of the silane coupling agent is preferably greater than orequal to 1 mass parts, more preferably 2 mass parts with respect tosilica by 100 mass parts. There is a tendency that the wear resistanceis likely to be lowered when the content of the silane coupling agent isless than 1 mass parts. Moreover, the content of the silane couplingagent is preferably less than or equal to 20 weight parts, morepreferably 15 weight parts. When the content of the silane couplingagent exceeds 20 weight parts, there is a tendency that the improvingeffect by blending of the silane coupling agent cannot be obtained andthe cost is increased.

Second Embodiment

In one embodiment of the present invention, the inner liner is made of apolymer laminate.

<Polymer Laminate>

The polymer laminate includes a first layer and a second layer.

(First Layer)

In Second Embodiment, the first layer of the polymer laminate may beused which is similar to the polymer sheet of First Embodiment.

(Second Layer)

In Second Embodiment, the second layer includes a thermoplastic resincomposition having thermoplastic elastomer and sulfur. The second layermay further include, in addition to the thermoplastic resin composition,a rubber component of at least one kind selected from the groupconsisting of natural rubber, isoprene rubber, and isobutylene-isoprenerubber.

(Thermoplastic Resin Composition)

The thermoplastic resin composition includes thermoplastic elastomer andsulfur. By adding sulfur to thermoplastic elastomer, a non-vulcanizationstickiness and a vulcanization adhesiveness with the first layer areimproved. Further, a non-vulcanization stickiness and a vulcanizationadhesiveness with an adjacent member such as a carcass or an insulationare also improved.

(Thermoplastic Elastomer)

The thermoplastic elastomer which can be used may be at least one kindselected from the group consisting of a styrene-isoprene-styrenetriblock copolymer, a styrene-isobutylene diblock copolymer, astyrene-butadiene-styrene triblock copolymer, astyrene-isoprene/butadiene-styrene triblock copolymer, astyrene-ethylene/butene-styrene triblock copolymer, astyrene-ethylene/propylene-styrene triblock copolymer, astyrene-ethylene/ethylene/propylene-styrene triblock copolymer, and astyrene-butadiene/butylene-styrene triblock copolymer. Thesethermoplastic elastomers may be an epoxy modified thermoplasticelastomer having an epoxy group. Among those, it is preferable to usethe styrene-isoprene-styrene triblock copolymer, the styrene-isobutylenediblock copolymer, or the epoxy modified styrene-butadiene-styrenetriblock copolymer. In the following, the styrene-isoprene-styrenetriblock copolymer, the styrene-isobutylene diblock copolymer, and theepoxy modified styrene butadiene styrene triblock copolymer will bedescribed.

(Styrene-Isoprene-Styrene Triblock Copolymer)

Since an isoprene block of the styrene-isoprene-styrene triblockcopolymer (in the following, also referred to as “SIS”) is a softsegment, the thermoplastic resin composition including SIS is likely toexhibit a vulcanization adhesion to the rubber component. Thus, when thethermoplastic resin composition including SIS is used for the polymerlaminate, since the polymer laminate is superior in an adhesiveness withan adjacent rubber forming the carcass or insulation, a pneumatic tirecapable of preventing the air-in and superior in the durability can beobtained.

The molecular weight of SIS is not particularly limited. However, inview of the rubber elasticity and moldability, it is preferable that theweight-average molecular weight according to the GPC method is greaterthan or equal to 100,000 and less than or equal to 290,000. When theweight-average molecular weight is less than 100,000, the tensilestrength is likely to be lowered. When the weight-average molecularweight exceeds 290,000, the extrusion performance is deteriorated.Therefore, it is not preferable.

It is preferable that the content of the styrene unit in the SIS isgreater than or equal to 10 mass % and less than or equal to 30 mass %in view of the stickiness, adhesiveness, and rubber elasticity.

It is preferable that SIS has a molar ratio of the isoprene unit and thestyrene unit (isoprene unit/styrene unit) of 90/10 to 70/30. In SIS, itis preferable that a degree of polymerization of each block isapproximately 500 to 5,000 for the isoprene block and approximately 50to 1,500 for the styrene block in view of the rubber elasticity andhandling.

SIS can be obtained by a general method for polymerizing a vinyl-basedcompound. For example, it can be obtained by, for example, the livingcationic polymerization method.

The second layer including SIS can be obtained by a general method ofmixing SIS, sulfur, and other additive in a Banbury mixer and forming asheet of thermoplastic resin and thermoplastic elastomer by extrusionand calender molding.

(Styrene-Isobutylene Diblock Copolymer)

Since the isobutylene block of the styrene-isobutylene-diblock copolymer(in the following, also referred to as “SIB”) is a soft segment, thethermoplastic resin composition including SIB is likely to exhibit avulcanization-adhesion to a rubber component. Thus, when thethermoplastic resin composition including SIB is used for the polymerlaminate, since the polymer laminate is superior in an adhesiveness withadjacent rubber forming a carcass and an insulation for example, theair-in can be prevented, and a pneumatic tire superior in the durabilitycan be obtained.

As SIB, it is preferable to use SIB having a straight chain shape inview of the rubber elasticity and the adhesiveness.

Although the molecular weight of SIB is not limited, it is preferablethat the weight-average molecular weight according to the GPC method isgreater than or equal to 40,000 and less than or equal to 120,000 inview of the rubber elasticity and the moldability. When theweight-average molecular weight is less than 40,000, the tensilestrength is likely to be lowered. When the weight-average molecularweight exceeds 120,000, the extrusion property is likely to bedeteriorated. Thus, it is not preferable.

It is preferable that the content of the styrene unit in SIB is greaterthan or equal to 10 mass % and less than or equal to 35 mass % in viewof the stickiness, the adhesiveness, and the rubber elasticity.

It is preferable that SIB has a molar ratio of the isobutylene unit andthe styrene unit (isobutylene unit/styrene unit) of 90/10 to 65/35. InSIB, it is preferable that a degree of polymerization for each block isapproximately 300 to 3,000 for the isobutylene block and approximately10 to 1,500 for the styrene block in view of the rubber elasticity andhandling.

SIB can be obtained by the general method for polymerizing a vinyl-basedcompound. For example, it can be obtained by the living cationicpolymerization method.

WO2005/033035 discloses a manufacturing method for obtaining SIB byadding methylcyclohexane, n-butyl chloride, and cumyl chloride to anagitator, cooling to −70° C., allowing a reaction to performed for twohours, adding a large amount of methanol to stop the reaction, andperforming vacuum-drying at 60° C.

The second layer including SIB can be obtained by a general method ofmixing SIB, sulfur, and other additive in the Banbury mixer, and forminga sheet of thermoplastic resin and thermoplastic elastomer by extrusionand calender molding.

(Epoxy Modified Styrene-Butadiene-Styrene Triblock Copolymer)

The epoxy modified styrene-butadiene-styrene triblock copolymer (in thefollowing, also referred to as “epoxy modified SBS”) is thermoplasticelastomer having a polystyrene block as a hard segment and a butadieneblock as a soft segment, and a non-saturated double-bond portionincluded in the butadiene block is epoxidated. Since epoxy modified SBShas a soft segment, the thermoplastic resin composition including epoxymodified SBS is likely to exhibit a vulcanization adhesion to the rubbercomponent. Thus, when the thermoplastic resin composition includingepoxy modified SBS is used for the polymer laminate for an inner liner,since the polymer laminate is superior in the adhesiveness with adjacentrubber forming a carcass or an insulation for example, the air-in can beprevented, and a pneumatic tire superior in the durability can beobtained.

Although the molecular weight of epoxy modified SBS is not particularlylimited, it is preferable that the weight-average molecular weightaccording to the GPC method is greater than or equal to 10,000 and lessthan or equal to 400,000 in view of the rubber elasticity and themoldability. When the weight-average molecular weight is less than10,000, the reinforcing effect may be lowered. When the weight-averagemolecular weight exceeds 400,000, the viscosity of the thermoplasticresin composition may be raised. Therefore, it is not preferable.

It is preferable that the content of the styrene unit in epoxy modifiedSBS is greater than or equal to 10 mass % and less than or equal to 30mass % in view of the stickiness, the adhesiveness, and the rubberelasticity.

It is preferable that epoxy modified SBS has a molar ratio of thebutadiene unit and the styrene unit (butadiene unit/styrene unit) of90/10 to 70/30. In epoxy modified SBS, it is preferable that a degree ofpolymerization of each block is approximately 500 to 5,000 for thebutadiene block and approximately 50 to 1,500 for the styrene block inview of the rubber elasticity and handling.

The second layer including epoxy modified SBS can be obtained by ageneral method of mixing SIB, sulfur, and other additive in the Banburymixer and forming a sheet of thermoplastic resin and thermoplasticelastomer by extrusion and calender molding.

(Rubber Component)

The second layer can include a rubber component in addition to thethermoplastic elastomer composition.

As the rubber component, rubber of at least one kind selected from thegroup consisting of natural rubber, isoprene rubber, andisobutylene-isoprene rubber can be used.

It is preferable that the content of the rubber component is greaterthan or equal to 20 mass % and less than or equal to 90 mass %, morepreferably greater than or equal to 30 mass % and less than or equal to80 mass % with respect to the sum total of the thermoplastic resincomposition and the rubber component. When it is less than 20 mass %,the second layer is less likely to exhibit a vulcanization adhesion tothe carcass layer. When it exceeds 90 mass %, the second layer and thecarcass layer are likely to exhibit a vulcanization adhesion too much.

(Sulfur)

Sulfur which is similar to that of First Embodiment can be used.

The content of sulfur is greater than or equal to 0.1 mass parts andless than or equal to 5 mass parts with respect to the thermoplasticelastomer by 100 mass parts. When the content of sulfur is less than 0.1mass parts, the crosslinking reaction may not occur. On the other hand,when the content of sulfur exceeds 5 mass parts, the crosslinkingdensity of the thermoplastic resin composition may be raised, and theviscosity may be raised. It is more preferable that the content ofsulfur is greater than or equal t0 0.3 mass parts and less than or equalto 3 mass parts.

(Additive of Thermoplastic Resin Composition)

In Second Embodiment, the thermoplastic resin composition constitutingthe polymer laminate for the inner liner can include additive such asstearic acid, zinc oxide, an anti-aging agent, and a vulcanizationaccelerator. These additives can be similar to those of FirstEmbodiment.

It is preferable that the content of the stearic acid is greater than orequal to 1 mass parts and less than or equal to 5 mass parts withrespect to the thermoplastic elastomer by 100 mass parts. When thecontent of the stearic acid is less than 1 mass parts, the vulcanizationmay not occur. On the other hand, when the content of the stearic acidexceeds 5 mass parts, the fracture strength of the thermoplastic resincomposition may be lowered. It is more preferable that the content ofthe stearic acid is greater than or equal to 1 mass parts and less thanor equal to 4 mass parts.

It is preferable that the content of zinc oxide is greater than or equalto 0.1 mass parts and less than or equal to 8 mass parts with respect tothe thermoplastic elastomer by 100 mass parts. When the content of zincoxide is less than 0.1 mass parts, the vulcanization may not beperformed. On the other hand, when the content of zinc oxide exceeds 8mass parts, the hardness of the thermoplastic resin composition may beraised, and the durability may be lowered. It is more preferable thatthe content of zinc oxide is greater than or equal to 0.5 mass parts andless than or equal to 6 mass parts.

It is preferable that the content of the anti-aging agent is greaterthan or equal to 0.1 mass parts and less than or equal to 5 mass partswith respect to the thermoplastic elastomer by 100 mass parts. When thecontent of the anti-aging agent is less than 0.1 mass parts, theanti-aging effect may not be obtained. On the other hand, when thecontent of the anti-aging agent exceeds 5 mass parts, the bloomingphenomenon may occur. It is more preferable that the content of theanti-aging agent is greater than or equal to 0.3 mass parts and lessthan or equal to 4 mass parts.

It is preferable that the content of the vulcanization accelerator isgreater than or equal to 0.1 mass parts and less than or equal to 5 massparts with respect to the thermoplastic elastomer by 100 mass parts.When the content of the vulcanization accelerator is less than 0.1 massparts, the vulcanization-accelerating effect may not be obtained. On theother hand, when the content of the vulcanization accelerator exceeds 5mass parts, the hardness of the thermoplastic resin composition may beraised, and the durability may be lowered. Further, the cost of rawmaterial of the thermoplastic resin composition is raised. It is morepreferable that the content of the vulcanization accelerator is greaterthan or equal to 0.3 mass parts and less than or equal to 4 mass parts.

(Thickness of Polymer Laminate)

In Second Embodiment, it is preferable that the polymer laminate has athickness T1 of 0.6 mm<T1≤4.0 mm. When the thickness of the polymerlaminate is less than or equal to 0.6 mm, a favorable operationstability cannot be obtained with a pneumatic tire having the polymersheet applied to an inner liner.

On the other hand, when the thickness of the polymer laminate exceeds4.0 mm, the tire weight and the rolling resistance are increased tolower the low fuel consumption performance. It is more preferable thatthe thickness of the polymer laminate is greater than or equal to 0.8 mmand less than or equal to 3.8 mm.

(Method for Manufacturing Polymer Laminate)

In Second Embodiment, the polymer laminate can be manufactured, forexample, by the following method.

The first layer is manufactured by the method similar to the method formanufacturing the inner liner polymer sheet of First Embodiment. Thesecond layer is manufactured by forming a sheet of the thermoplasticresin composition by the extrusion and calender molding. The polymerlaminate is manufacture by attaching the first layer and the secondlayer to each other.

Moreover, it can be manufactured by a laminate extrusion or aco-extrusion of pellets of the polymer composition and the thermoplasticresin composition.

<Tread>

In the present embodiment, a tread can be used which is similar to thetread of First Embodiment.

<Method for Manufacturing Pneumatic Tire>

The pneumatic tire according to the first embodiment of the presentinvention can be manufactured, for example, by the following method.

A green tire is manufactured by applying the polymer sheet and thepolymer laminate described above to the inner liner portion.

When the polymer sheet is used, it is so arranged that the polymer sheetforming inner liner 9 and carcass 61 are arranged to contact with eachother as shown in FIG. 2, for example.

When the polymer laminate is used, it is arranged toward an outer sidein the radius direction of the tire so that a second layer PL2 of thepolymer laminate comes in contact with carcass 61 as shown in FIG. 3,for example.

With such an arrangement, in the tire vulcanization step, the secondlayer and an adjacent member such as a carcass or an insulation canexhibit a vulcanization adhesion. Thus, since the inner layer and theadjacent member are favorably adhered in the obtained pneumatic tire,superior air permeation resistance and durability can be provided.

Next, the green tire is mounted to a die, and pressed and heated by abladder at 150 to 180° C. for 3 to 50 minutes, so that the vulcanizedtire is obtained. Next, the obtained vulcanized tire is preferablycooled at 50 to 120° C. for 10 to 300 seconds.

The pneumatic tire has a polymer sheet or a polymer laminate applied tothe inner liner. Since SIBS, SIS, SIB, epoxy modified SBS, and the likeconstituting the polymer sheet or polymer laminate are thermoplasticresin, when for example heated to 150 to 180° C. in the step ofobtaining the vulcanized tire, it is rendered to be in a softened statein the die. Since the thermoplastic resin in the softened state improvesthe reactivity more than in the solid state, it is welded to theadjacent member. In other words, the inner liner in contact with anouter surface of the expanded bladder is softened by heating and weldedto the bladder. If the vulcanized tire is attempted to be taken out fromthe die in the state where the inner liner and the outer surface of thebladder are welded, the inner liner is peeled off from an adjacentinsulation or carcass, so that the air-in phenomenon may occur.Moreover, the shape of the tire itself may be deformed.

Therefore, by quenching the obtained vulcanized tire immediately at orless than 120° C. for 10 seconds or longer, the thermoplastic resin usedfor the inner liner can be solidified. When the thermoplastic resin issolidified, the welding between the inner liner and the bladder iseliminated, so that peeling performance at the time of taking vulcanizedtire from the die is improved.

It is preferable that the cooling temperature is 50 to 120° C. When thecooling temperature is less than 50° C., it would be necessary toprepare a special cooling medium, which may deteriorate theproductivity. When the cooling temperature exceeds 120° C., thethermoplastic resin is not sufficiently cooled, and the inner linerremains welded to the bladder at the time of releasing from the die, sothat the air-in phenomenon may occur. It is more preferable that thecooling temperature is 70 to 100° C.

It is preferable that the cooling time is 10 to 300 seconds. If thecooling time is less than 10 seconds, the thermoplastic resin is notsufficiently cooled, and the inner liner remains welded to the bladderat the time of releasing from the die, so that the air-in phenomenon mayoccur. When the cool time exceeds 300 seconds, the productivity isdeteriorated. It is more preferable that the cool time is 30 to 180seconds.

It is preferable that the step of cooling the vulcanized tire isperformed after cooling the bladder. Since the bladder is hollow, acooling medium adjusted to the cooling temperature can be introduced tothe bladder after the vulcanization step is terminated.

The step of cooling the vulcanized tire can be performed by providing acooling structure to the die while cooling the bladder.

As the cooling medium, it is preferable to use one or more kind selectedfrom the group consisting of air, steam, water, and oil. Among those, itis preferable to use water which is superior in the cooling efficiency.

Example

<Consideration of Polymer Sheet>

(Manufacturing Polymer Sheet)

According to the blending formula shown in Table 1, each compoundingagent was placed into the two-axis extruder (screw diameter: φ50 mm,L/D: 30, cylinder temperature: 200° C.), and kneaded at 200 rpm to forma pellet. The obtained pellet was placed into the T-die extruder (screwdiameter: φ80 mm, L/D: 50, die grip width: 500 mm, cylinder temperature:220° C., film gauge: 4.0 mm) to create a polymer sheet having athickness of 4.0 mm.

The obtained polymer sheet was used to conduct the following evaluation.

(Non-Vulcanization Stickiness to Carcass Layer)

A sheet of the carcass layer (blend: styrene-butadiene rubber by 100mass parts, carbon black by 50 mass parts, sulfur by 2 mass parts,thickness: 2.0 mm) was prepared.

The polymer sheet and the sheet of the carcass layer are attached toeach other, and retained at 100 gf for 30 seconds, and thereafter theforce required for peeling was measured as the non-vulcanizationstickiness. With the following formula, a non-vulcanization stickinessfor each manufacturing example was presented as an index withManufacturing Example 1 as a reference (100). It shows that anon-vulcanization stickiness is stronger as a non-vulcanizationstickiness index is greater, and thus it is preferable.(non-vulcanization stickiness index)=(non-vulcanization stickiness ofeach Manufacturing Example)/(non-vulcanization stickiness ofManufacturing Example 1)×100

(Vulcanization Adherence with Carcass Layer)

The polymer sheet and the sheet of the carcass layer are attached toeach other and heated at 170° C. for 20 minutes to manufacture a samplefor a vulcanization adherence measurement. The peel force was measuredby a tensile peeling test to determine a vulcanization adherence. Withthe following formula, a vulcanization adherence of each manufacturingexample was presented as an index with Manufacturing Example 1 as areference (100). It represents that a vulcanization adherence isstronger as a vulcanization adherence index is greater, and thus it ispreferable.(vulcanization adherence index)=(vulcanization adherence of eachManufacturing Example)/(vulcanization adherence of Manufacturing Example1)×100

The result is shown in Table 1.

TABLE 1 Manufacturing Examples 1 2 3 4 5 6 7 8 9 10 11 12 13 14 BlendingSIBS⁽*¹⁾ — — 2 2 2 20 20 20 80 80 80 90 90 90 (mass NR⁽*²⁾ 30 50 98 — —80 — — 20 — — 10 — — parts) IR⁽*³⁾ — — — 98 — — 80 — — 20 — — 10 —IIR⁽*⁴⁾ 70 — — — 98 — — 80 — — 20 — — 10 SBR⁽*⁵⁾ — 50 — — — — — — — — —— — — Carbon black⁽*⁶⁾ 50 100 — — — — — — — — — — — — Oil⁽*⁷⁾ 10 10 — —— — — — — — — — — — Wax⁽*⁸⁾ 2 2 — — — — — — — — — — — — Anti-agingagent⁽*⁹⁾ 2 2 1 1 1 1 1 1 1 1 1 1 1 1 Stearic acid⁽*¹⁰⁾ 2 2 3 3 3 3 3 33 3 3 3 3 3 Oxidized zinc⁽*¹¹⁾ 4 3 5 5 5 5 5 5 5 5 5 5 5 5 Sulfur⁽*¹²⁾0.5 1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Vulcanization 1 21 1 1 1 1 1 1 1 1 1 1 1 accelerator⁽*¹³⁾ Evaluation Non-vulcanization100 110 95 95 92 80 80 77 50 50 47 40 40 35 stickiness index withcarcass layer Vulcanization 100 110 95 95 92 80 80 77 55 55 52 45 45 40adhesiveness index with carcass layer (Note 1) SIBS: “SIBSTAR 102T”manufactured by Kaneka Corporation (styrene-isobutylene-styrene triblockcopolymer, weight-average molecular weight of 100,000, styrene unitcontent of 25 mass %, Shore A hardness of 25). (Note 2) NR: naturalrubber, TSR 20. (Note 3) IR: “Nipol IR2200” manufactured by ZEONCorporation. (Note 4) IIR: “Exxon Chlorobutyl 1066” manufactured byExxon Mobil Corporation. (Note 5) SBR: “E15” manufactured by Asahi KaseiCorporation. (Note 6) Carbon black: “SEAST V” manufactured by TokaiCarbon Co., Ltd. (N660, nitrogen absorption specific surface area: 27m2/g). (Note 7) Oil: “Process X-260” manufactured by Japan EnergyCorporation. (Note 8) Wax: “Sunnock N” manufactured by Ouchi ShinkoChemical Industrial Co., Ltd. (Note 9) Anti-aging agent: “Antigene 6C”manufactured by Sumitomo Chemical Co., Ltd. (N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine). (Note 10) Stearic acid: “stearic acid“Tsubaki”” manufactured by NOF Corporation. (Note 11) Zinc oxide: “ZincOxide” manufactured by Mitsui Mining & Smelting Co., Ltd. (Note 12)Sulfur: “Powder Sulfur” manufactured by Karuizawa Sulfur Ltd. (Note 13)Vulcanization accelerator: “Nocceler DM” manufactured by Ouchi ShinkoChemical Industrial Co., Ltd. (di-2-benzothiazolyl disulfide).

(Evaluation Result)

Manufacturing Examples 3 to 14 represent polymer sheets including SIBSand one kind selected from the group consisting of natural rubber,isoprene rubber, and isobutylene-isoprene rubber. As the content of SIBSincreased, the non-vulcanization stickiness and the vulcanizationadherence with the carcass layer were lowered. Particularly in Examples12 to 14, the non-vulcanization stickiness and the vulcanizationadherence with the carcass layer were significantly lowered as comparedto Manufacturing Example 1.

(Manufacturing Pneumatic Tire)

Polymer sheets having the blending similar to those of Manufacturingexamples 1 to 11 were prepared. The thicknesses of the polymer sheetswere set to have the thicknesses shown in Table 2. Green tires wereprepared by applying the polymer sheets to the inner liners of thetires. The vulcanized tires having a 195/65R15 size were manufactured bypress-molding the green tires in the die at 170° C. for 20 minutes.After cooling the vulcanized tire at 100° C. for 3 minutes, thevulcanized tires were taken out from the die to obtain the pneumatictire.

The obtained pneumatic tires were used to conduct the followingevaluation.

(Air Permeation Resistance)

The manufactured tire having the 195/65R15 size was assembled to the JISStandard Rim 15x6JJ, and an initial air pressure of 300 Kpa wascontained, and the tire was left at a room temperature for 90 days, andthen a lowering rate of the air pressure (%/month) was calculated. Withthe following formula, the air permeation resistance of each Example andComparative example was presented by an index with Comparative Example1-9 as a reference (100). As the index is smaller, the air permeabilityis smaller, thus it is preferable.(air permeation resistance index)=(lowering rate of air pressure in eachExample and Comparative Example)/(lowering rate of air pressure inComparative Example 1-9)×100

(Rolling Resistance)

A rolling resistance testing machine manufactured by Kobe Steel, Ltd.was used to assemble the manufactured pneumatic tire having the195/65R15 size to the JIS Standard Rim 15x6JJ, and the tire traveled ata room temperature (38° C.) under the condition having the load of 3.4kN, the air pressure of 230 kPa, and the velocity of 80 km/hour, tomeasure the rolling resistance. With the following formula, the rollingresistance of each Example and Comparative Example was presented by anindex with Comparative Example 1-9 as a reference (100). As the rollingresistance index is greater, the rolling resistance is reduced, thus itis preferable.(rolling resistance index)=(rolling resistances of Comparative Example1-9)/(rolling resistance of each Example and Comparative Example)×100

(Operation Stability)

The pneumatic tires were mounted to all of wheels of a vehicle (FF2000ccmade in Japan) and the vehicle ran the test course, so that theoperation stability was evaluated in accordance with a driver's sensualevaluation. The evaluation was conducted with 10 points as full points,and the relative evaluation was conducted with Comparative Example 1-9scored 6 points. It would be favorable as the evaluation point isgreater.

The test result is shown in Table 2.

TABLE 2 Examples Comparative Examples 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-81-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 Polymer Manu- 6 6 7 8 9 9 10 116 6 7 8 9 9 10 11 1 2 sheet facturing Example Thickness 1.6 2.0 0.7 4.02.0 3.0 4.0 0.7 0.6 5.0 0.6 5.0 0.5 5.0 5.0 0.5 1.0 1.0 (mm) Eval- Air80 70 100 40 75 65 55 105 100 30 105 30 110 45 50 110 100 150 uationper- meation resistance index Rolling 120 110 140 100 115 110 105 135125 80 143 80 140 95 95 140 100 80 resistance index Operation 7 8 6 9 88.5 9 6 5 9 5 9 5 9 9 5 6 7 stability index

(Evaluation Result)

Examples 1-1 to 1-8 are pneumatic tires using polymer sheets having athickness of 0.7 mm to 4.0 mm. The tires had an air permeationresistance which is equal to or higher than Comparative Example 1-9, andthe rolling resistance was reduced, and the operation stability wasimproved.

Comparative Examples 1-1, 1-3, 1-5, and 1-8 are pneumatic tires usingpolymer sheets having a thickness of 0.5 mm to 0.6 mm. As compared toComparative Example 1-9, there is a tendency that the operationstability and the air permeation resistance are worse.

Comparative Examples 1-2, 1-4, 1-6, and 1-7 are pneumatic tires usingpolymer sheets having a thickness of 5.0 mm. As compared to ComparativeExample 1-9, the rolling resistance was increased.

<Consideration of Second Layer>

(Manufacturing of SIB)

Methylcyclohexane (dried with molecular sieves) of 589 mL, n-butylchloride (dried with molecular sieves) of 613 mL, and cumyl chloride of0.550 g were added to a 2 L reaction container having an agitator. Aftercooling the reaction container to −70° C., α-picoline (2-methylpyridine)of 0.35 mL and isobutylene of 179 mL were added. Titanium tetrachlorideof 9.4 mL was further added, and the polymerization was stared. Thesolution was agitated at −70° C. and allowed to react for 2.0 hours.Next, styrene of 59 mL was added to the reaction container, and thereaction was continued for 60 minutes. After that, a large amount ofmethanol was added to stop the reaction. After a solvent and the likewere removed from the reaction solution, the polymer was dissolved intoluene and washed twice. The toluene solution was added to a methanolmixture to deposit the polymer, and the obtained polymer was dried at60° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer.

(Manufacturing of Thermoplastic Resin Sheet)

After mixing each compounding agent in accordance with the blendingformulas shown in Table 3, thermoplastic resin sheets where manufacturedby the method similar to that for the polymer sheets described above.The following evaluation was conducted for the obtained thermoplasticresin sheets.

(Non-Vulcanization Stickiness to Carcass Layer)

The non-vulcanization stickiness was measured by the method which issimilar to that for the polymer sheets described above, and anon-vulcanization stickiness for each Manufacturing Example waspresented by an index with Manufacturing Example 1 as a reference (100).As the non-vulcanization stickiness index is greater, thenon-vulcanization stickiness is stronger, thus it is preferable.(non-vulcanization stickiness index)=(non-vulcanization stickiness ofeach Manufacturing Example)/(non-vulcanization stickiness ofManufacturing Example 1)×100

(Vulcanization Adherence to Carcass Layer)

The vulcanization adherence was measured by the method which is similarto that for the polymer sheets described above, and the vulcanizationadherence for each Manufacturing Example was presented by an index withManufacturing Example 1 as a reference (100). As the vulcanizationadherence index is greater, the vulcanization adherence is stronger,thus it is preferable.(vulcanization adherence index)=(vulcanization adherence for eachManufacturing Example)/(vulcanization adherence for ManufacturingExample 1)×100

(Evaluation Result)

The test result is shown in Table 3.

TABLE 3 Manufacturing Examples 15 16 17 18 19 20 Blending (mass parts)SIS⁽*¹⁴⁾ 100 100 — — — — SIB⁽*¹⁵⁾ — — 100 100 — — Epoxidated SBS⁽*¹⁶⁾ —— — — 100 100 Stearic acid⁽*¹⁰⁾ — 3 — 3 — 3 Oxidized zinc⁽*¹¹⁾ — 5 — 5 —5 Anti-aging agent⁽*⁹⁾ — 1 — 1 — 1 Vulcanization accelerator⁽*¹³⁾ — 1 —1 — 1 Sulfur⁽*¹²⁾ — 0.5 — 0.5 — 0.5 Evaluation Non-vulcanizationstickiness 50 80 50 95 55 100 index with carcass layer Vulcanizationadhesiveness 50 80 50 95 55 100 index with carcass layer (Note 9) to(Note 13) These are the same as Table 1. (Note 14) SIS: “D1161JP”manufactured by Kraton Polymers, Inc. (styrene-isoprene-styrene triblockcopolymer, weight-average molecular weight of 150,000, styrene unitcontent of 15 mass %). (Note 15) SIB: SIB obtained above (Manufacturingof SIB) (styrene-isobutylene diblock copolymer, weight-average molecularweight of 70,000, styrene unit content of 15 mass %). (Note 16) Epoxymodified SBS: “Epofriend A1020” manufactured by Daicel ChemicalIndustry, Ltd. (epoxy modified styrene-butadiene-styrene, weight-averagemolecular weight of 100,000, weight per epoxy equivalent of 500).

Manufacturing Examples 16, 18, and 20 are thermoplastic resin sheetsmade of a thermoplastic resin component including SIS, SIB, or epoxymodified SBS and additive such as sulfur. The thermoplastic resin sheetshad sufficient non-vulcanization stickiness and vulcanization adherencewith a carcass layer.

Manufacturing Examples 15, 17, and 19 are thermoplastic resin sheetsmade of a thermoplastic resin composition made of SIS, SIB, or epoxymodified SBS and not including additive. The thermoplastic resin sheetshad insufficient vulcanization adherence with a carcass layer.

<Consideration of Polymer Laminate>

(Manufacturing of Polymer Laminate)

Each compounding agent was placed into the two-axis extruder (screwdiameter: φ50 mm, L/D: 30, cylinder temperature: 200° C.) in accordancewith the blending formula of Manufacturing Example numbers shown inTable 4, and kneaded at 200 rpm to form a pellet. The obtained pelletwas placed into a co-extruder (cylinder temperature: 200° C.) to obtaina polymer laminate constituted of two layers. A thickness of eachpolymer laminate was adjusted to have a thickness shown in Table 4.

(Manufacturing of Pneumatic Tire)

The obtained polymer laminate was applied to the inner liner portion ofthe tire to prepare a green tire. The polymer laminate had a first layerarranged at the most inner side in the radial direction of the greentire, and a second layer arranged to come in contact with a carcasslayer of the green tire. The green tire was press-molded in the die at170° C. for 20 minutes to manufacture a vulcanized tire having the196/65R15 size. After cooling the vulcanized tire at 100° C. for 3minutes, the vulcanized tire was taken out from the die to obtain thepneumatic tire.

The obtained pneumatic tire was used to conduct the followingevaluation.

(Air Permeation Resistance)

By the method similar to Example 1-1, a lowering rate of an air pressureof the pneumatic tire was measured. With the following formula, the airpermeation resistance for each Example and Comparative Example waspresented by an index with Comparative Example 1-9 as a reference (100).As the index is smaller, the air permeability is smaller, thus it ispreferable.(air permeation resistance index)=(lowering rate of air pressure foreach Example and Comparative Example)/(lowering rate of air pressure forComparative Example 1-9)×100

(Rolling Resistance)

A rolling resistance of the pneumatic tire was measured by the methodwhich is similar to that for Example 1-1. With the following formula,the rolling resistance of the pneumatic tire having each polymerlaminate was presented by an index with Comparative Example 1-9 as areference (100). As the rolling resistance index is greater, the rollingresistance is reduced, and thus it is preferable.(rolling resistance index)=(rolling resistance of Comparative Example1-9)/(rolling resistance of each Example and Comparative Example)×100

(Operation Stability)

The pneumatic tires are mounted to all of wheels of a vehicle (FF2000ccmade in Japan), and the operation stability was evaluated based on adriver's sensual evaluation. The evaluation was made with 10 points asfull points, and a relative evaluation was conducted with ComparativeExample 1-9 as scored 6 points. It is preferable when the evaluationpoint is greater.

The test result is shown in Table 4.

TABLE 4 Examples Comparative Examples 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-82-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 Polymer Manu- First 6 6 7 8 9 10 10 11 66 7 8 9 9 10 11 Laminate facturing Layer Example Second 16 18 20 16 1820 18 16 20 16 18 20 16 18 20 16 Number Layer Total thickness 0.7 4.00.7 4.0 2.0 3.0 4.0 3.0 0.6 5.0 0.5 5.0 0.5 5.0 5.0 0.4 (mm) EvaluationAir permeation 100 40 100 45 70 65 50 50 100 30 105 35 110 30 35 100resistance index Rolling resistance 140 100 145 100 120 110 100 105 13080 140 75 135 75 80 120 index Operation stability 6 8.5 6 9 7.5 8 8 8.55 8.5 5 8.5 5 9 9 4

(Evaluation Result)

Examples 2-1 to 2-8 are pneumatic tires using the polymer sheets ofManufacturing Examples 6 to 11 as a first layer and thermplastic resinsheets of Manufacturing Examples 16, 18, and 12 as a second layer, andapplying the polymer laminate having a thickness of 0.7 mm to 4.0 mm tothe inner liner. The tires had an air permeation resistance equal to orhigher than Comparative Example 1-9, and the rolling resistance wasreduced, and the operation stability was improved.

Comparative Examples 2-1, 2-3, 2-5, and 2-8 had a polymer laminatehaving a thickness of 0.4 mm to 0.6 mm. The tire exhibited worseoperation stability as compared to Comparative Example 1-9.

Comparative Examples 2-2, 2-4, 2-6, and 2-7 had a polymer laminatehaving a thickness of 5.0 mm. The tire had an increased rollingresistance as compared to Comparative Example 1-9.

It should be understood that the embodiments and examples disclosedherein are illustrative and non-restrictive in every respect. The scopeof the present invention is defined by the terms of the claims, ratherthan the description of the embodiments set forth above, and is intendedto include any modifications within the scope and meaning equivalent tothe terms of the claims.

REFERENCE SIGN LIST

1 pneumatic tire; 2 tread portion; 3 side wall portion; 4 bead portion;5 bead core; 6, 61 carcass; 7 belt layer; 8 bead apex; 9 inner liner;PL1 first layer; PL2 second layer.

The invention claimed is:
 1. A pneumatic tire for passenger carscomprising an inner liner made of a polymer laminate, said polymerlaminate consisting of a first layer and a second layer, said firstlayer being made of a polymer composition, said polymer compositionincluding: a polymer component of a styrene-isobutylene-styrene triblockcopolymer by greater than or equal to 10 mass % and less than or equalto 40 mass %, and a rubber component of at least one kind selected fromthe group consisting of natural rubber, isoprene rubber, andisobutylene-isoprene rubber by greater than or equal to 60 mass % andless than or equal to 90 mass %, said polymer composition includingsulfur by greater than or equal to 0.1 mass parts and less than or equalto 5 mass parts with respect to said polymer component by 100 massparts, said second layer including a thermoplastic resin composition,and said thermoplastic resin composition including: a thermoplasticelastomer, and sulfur by greater than or equal to 0.1 mass parts andless than or equal to 5 mass parts with respect to thermoplasticelastomer by 100 mass parts, and said polymer laminate having athickness T2 of 2.0 mm≤T2≤3.0 mm, wherein said thermoplastic elastomeris at least one kind selected from the group consisting of astyrene-isoprene-styrene triblock copolymer, a styrene-isobutylenediblock copolymer, a styrene-butadiene-styrene triblock copolymer, astyrene-isoprene/butadiene-styrene triblock copolymer, astyrene-ethylene/butene-styrene triblock copolymer, astyrene-ethylene/propylene-styrene triblock copolymer, astyrene-ethylene/ethylene/propylene-styrene triblock copolymer, astyrene-butadiene/butylene-styrene triblock copolymer, and epoxymodified thermoplastic elastomers thereof.
 2. The pneumatic tireaccording to claim 1, wherein said styrene-isoprene-styrene triblockcopolymer has a styrene unit content of greater than or equal to 10 mass% and less than or equal to 30 mass %.
 3. The pneumatic tire accordingto claim 1, wherein said styrene-isobutylene diblock copolymer has astraight-chain shape, and has a styrene unit content of greater than orequal to 10 mass % and less than or equal to 35 mass %.
 4. The pneumatictire according to claim 1, wherein said epoxy modifiedstyrene-butadiene-styrene triblock copolymer has a styrene unit contentof greater than or equal to 10 mass % and less than or equal to 30 mass%, and an epoxy equivalent of greater than or equal to 50 and less thanor equal to 1,000.
 5. The pneumatic tire according to claim 1, whereinsaid thermoplastic resin composition further includes stearic acid bygreater than or equal to 1 mass parts and less than or equal to 5 massparts, zinc oxide by greater than or equal to 0.1 mass parts and lessthan or equal to 8 mass parts, an anti-aging agent by greater than orequal to 0.1 mass parts and less than or equal to 5 mass parts, and avulcanization accelerator by greater than or equal to 0.1 mass parts andless than or equal to 5 mass parts with respect to said thermoplasticelastomer by 100 mass parts.
 6. The pneumatic tire according to claim 1,wherein said second layer further includes, in addition to saidthermoplastic resin composition, a rubber component of at least one kindselected from the group consisting of natural rubber, isoprene rubber,and isobutylene-isoprene rubber, and includes said rubber component bygreater than or equal to 20 mass % and less than or equal to 90 mass %with respect to a sum total of said thermoplastic resin composition andsaid rubber component.
 7. The pneumatic tire according to claim 1,wherein said styrene-isobutylene-styrene triblock copolymer has astyrene unit content of greater than or equal to 10 mass % and less thanor equal to 30 mass %.
 8. The pneumatic tire according to claim 1,wherein said polymer composition further includes stearic acid bygreater than or equal to 1 mass parts and less than or equal to 5 massparts, zinc oxide by greater than or equal to 0.1 mass parts and lessthan or equal to 8 mass parts, an anti-aging agent by greater than orequal to 0.1 mass parts and less than or equal to 5 mass parts, and avulcanization accelerator by greater than or equal to 0.1 mass parts andless than or equal to 5 mass parts with respect to said polymercomponent by 100 mass parts.
 9. The pneumatic tire according to claim 1,wherein a tread of said pneumatic tire is made of a rubber compositionincluding styrene-butadiene rubber by greater than or equal to 50 mass %in the rubber component.
 10. The pneumatic tire according to claim 1,wherein the polymer laminate includes stearic acid, oxidized zinc,sulfur and a vulcanization accelerator.